Prefabricated units are commonly used in the construction of buildings, such as homes, apartments and office buildings. The prefabricated unit is positioned within a opening provided in the frame of the building and is secured to the opening by nailing fins that extend outwardly from the exterior of the frame unit. If the nailing fins are provided with the frame unit, difficulties are encountered in storage and transport due to the susceptibility of the nailing fins to be bumped and broken. Where separate nailing fins are provided, they must be matched to the appropriate frame section and inserted as needed for securing the unit to the frame of the house.